Apparatus for heat treating metallic articles

ABSTRACT

The method and apparatus for heat treating metallic articles, wherein the articles are embedded in a ceramic fiber work holder such that the embedded portion is prevented from reaching a temperature during the heat treating operation that produces a hardening action thereon, the non-hardened portion of the articles being easily stamped or marked with identifying indicia thereon after the heat treating operation.

Dec. 5, 1972 United States Patent Paulson .263/2 R ....2e3/2 R 3/1970Rea...............,........................263/2R 4/1956Wallerius.............................

L e h C n .w B 5 3 9 l 944 663 4 6 69 499 7 9 44 2 3 PrimaryExaminer-John J. Camby Attorney-Salter & Michaelson The method andapparatus for heat treating metallic varticles, wherein the articles areembedded in a 22 Filed: July 13,1970

[211 Appl. No.: 61,031

ABSTRACT Related US. Application Data [62] Division of Ser. No.675,437," Oct. 16, l967,'Pat.

ceramic fiber work holder such that the embedded portion is preventedfrom reaching a temperature durmg the heat treating operation thatproduces a hardening actionthereon the non-hardened portion [52] US.[51] Int.

27 3 02 of the articles being easily stamped or marked with identifyingindicia thereon after the heat treating [58] Field of Search..i263/2 R,47 R, 47 A; 266/6 PC operation.

1 Claim, 2 Drawing Figures References Cited UNITED STATES PATENTS2,086,290 Bedford................................263/2 R PATENTED 519??3,704,871

SHEET 2 [1F 2 APPARATUS FOR HEAT TREATING METALLIC ARTICLES This is adivision of application Ser. No. 675,437, filed Oct. 16,1967 now U.S.Pat. No. 3,615,927.

BACKGROUND OF THE INVENTION The present invention has particularapplication in the heat treatment of metallic articles wherein a portionof the article is adapted'to be marked with an identifyingname, numberor symbol, one example of this kind of a metallic article being anelongated tool such as a drill. Prior to the instant invention, specialprocedures were required in the heat treatment of tools such as drillsif it was necessary to maintain the shank of the drill soft enough tohave identifying indicia or lettering imprinted therein. In those priorknown furnaces that employed a salt bath for hardening, the shanks ofthe drills were physically held in insulated grip tongs while the fluteswere lowered into the hot salt. After the heat treatment, the fluteswerequenched in air or in a lower temperature salt or in oil. However,after the quenching operation, a cleaning procedure was necessary beforetempering and marking.

In another technique wherein the drill blanks were hardened in a saltbath, the blanks were allowed to be heat treated throughout the lengththereof, and after the heat treatment operation and the cooling of theblanks, they were then subjected to a second treatment to soften theshanks. This treatment usually consisted of fixing the blanks in tongsand then, lowering the shank into hot lead or salt. Thereafter, acleaning operation was also necessary before further processing.

In another prior known procedure where an atmosphere controlled furnacewas utilized, the drills or drill blanks were loaded in trays or basketsand then placed in the furnace for the heat treatment thereof. After theheat treatment operation and the passage of the work load into a coolingchamber, the drills were file-hard all over. Although the drills wereclean after this heat treatment procedure, they still had to beprocessed further to soften the shanks thereof. This further operationusually discolored the shanks and required a separate cleaning step.

Although these prior known procedures eventually accomplished thepurpose of enabling the drill shank to be marked with appropriateidentifying indicia, the additional steps involved, either in softeningthe shank or in cleaning the shank, necessarily increased the cost ofmanufacture of the articles and further caused considerable delays inobtaining the finished product.

SUMMARY OF THE INVENTION The present invention provides for the heattreatment of metallic articles in an atmosphere furnace wherein theshank portion of the articles are sufficiently protected so that duringthe heat treatingoperation they do not reach that temperature thatresults in a file-hard surface. This is accomplished by locating theshanks of the articles in a ceramic fiber block which acts as aninsulator and prevents the shanks of the articles located therein frombeing heated to the same temperature as the exposed portions thereof.After the heat treating operation, the ceramic fiber block with themetallic articles located therein is quickly moved to a cooling chamberwhere the articles are cooled by a fan that circulates a coolingatmosphere within the cooling chamber. Thus, the atmosphere that isforced over and around the articles removes the heat from the articlesquickly enough so that the portions that are embedded in the ceramicfiber block never reach the hardening temperature.

Accordingly, it is an object of the invention to teach a method andprovide apparatus for heat treating metallic articles, wherein a portionof the articles is insulated during the heat treating operation so as tobe prevented from becoming file hardened.

Another object of the invention is to teach a method of preventing aportion of a metallic article from becoming file hardened during theheat treating operation so thatthe non-hardened portion can be suitablymarked or stamped with identifying indicia thereon.

Still another object isto provide apparatus for heat treating metallicarticles that includes a ceramic fiber block in which the articles areembedded, the embedded'portion of each article being effectivelyinsulated during the heat treating operation and thereby being preventedfrom becoming file hardened so that the surface thereof may besuitablymarked with identifying indicia.

Still another object is to provide apparatus for heat treating metallicarticles, wherein the articles are quickly quenched in a circulatingmedium, thereby preventing a portion of the articles that had beeninsulated duringthe heat treating process from becoming file hardened.

Other objects, features and advantages of the invention will becomeobvious as the description thereof proceeds when considered inconnection with the accompanying illustrative drawings.

DESCRIPTION OF THE DRAWINGS tion of the ceramic fiber block showing thelocation of the metallic. articles therein during the heat treatingoperation.

DESCRIPTION OF THE INVENTION Referring now to the drawings andparticularly to FIG. 1, a furnace assemblyis illustrated and isgenerally indicated at 10. The furnace assembly l0.comprises a furnaceunit 12 having a heat treating chamber 13 located therein. The furnaceunit 12 is comprised of conventional insulating blocks and heatingelements which do not form any part of the present invention. Verticallymovable doors 15 and 16 are adapted to seal openings 11 and 14 locatedat the ends of the heat treating chamber 13 during the heat treatingoperation and any conventional means may be employed for moving thesedoors to the open position thereof.

Located adjacent to the furnace unit 12 and communicating therewiththrough a duct 17 is a cooling generally indicated at 18. The coolingstation 18 in cludes an outer jacket 25 that envelopes a cylinder 27 inwhich a cooling chamber 19 is defined. A cooling medium may becirculated within the jacket and mounted in the cooling chamber 19 is afan 20 that is driven by a motor 21 for circulating a conditioning gaswithin the cooling chamber. The conditioning gas such as hydrogen,enters the cooling chamber through an inlet pipe 22, and it isunderstood that a similar conditioning gas is also circulated in theheat treating chamber 13 during the heat treating operation.

Mounted for movement on a track 24 that extends through the furnace unit12' and into the cooling chamber 19 is a tray generally indicated at 26on which a work basket 28 is located. The work basket 28, as will bedescribed, contains a work holder therein in the form of a ceramic fiberblock generally indicated at 30, the ceramic fiber block 30 beingespecially designed for retaining the articles therein that are to beheat treated. The tray 26 with the work basket 28 located thereon isadapted to be moved from the heat treating chamber 13 into the coolingchamber 18 after the heat treating operation in which area the articlesare quickly quenched by introducing the conditioning gas through theinlet pipe 22 and rapidly circulating the conditioning gas within thecooling chamber by means of the fan 20. Although not shown, the basket28 and the tray 26 are movable by any convenient means such as a pushrod to and from the heat treating chamber 13 and the cooling chamber 18.If required, a conveyor belt may also be employed for carrying the tray26 through the heat treating chamber 13 and cooling chamber 19 in whichcase the heat treating operation would be continuous. As further shownin FIG. 7, a duct 23 also communicates with the cooling chamber 19 andmay be employed as a discharge area for removing the block 30 and thearticles embedded therein from the cooling chamber following the coolingcycle. Any suitable door or gate will be located in the duct 23 to sealthe cooling chamber from the outside atmosphere.

Referring now to FIG. 2, the tray 26 and basket 28 as mounted thereonare shown in detail, and, as illustrated, the tray 26 includes spacedparallel members 32 on which similar cross members 32 are fixed to forma framework. End cross members 34 are joined to the ends of one set ofthe members 32 and are fixed to vertical brackets 36. Upstanding pins 38are joined to the ends of the members 32 and define the end limitingmeans for retaining the basket 28 therebetween. Longitudinally extendingmembers 39 support the cross members 32 and are received on the track 24for movement thereon.

One of the features of the invention is providing for the heat treatmentof metallic articles wherein a portion of each article is effectivelyembedded or insulated during the heat treating operation so as to beprevented from reaching the austenitizing or hardening temperature. Bypreventing the embedded portion of the articles from reaching thehardening temperature, this portion may later be suitably marked withidentifying indicia without the requirement of additional procedures forsoftening a portion of the metal and cleaning the metal thereafter.

In the present invention, it is contemplated that metallic articles suchas drills will be heat treated, and, as shown in FIG. 2, a plurality ofdrill blanks of various lengths are illustrated and are indicated at 40,42 and 43. The drill blank which is representative of one size of adrill includes a first portion indicated at 44 and a' second portionindicated at 46, the first portion 44 defining the portion of the drillblank that will be formed with the flutes thereon and the second portion46 defining the shank of the drill. It is conventional to mark the shank46 of the drill with identifying indicia, and it is for this purposethat the present invention provides for insulating the shank portion 46of the drill during the heat treating operation so as to prevent theportion from reaching the hardening temperature.

In order to prevent the shank portion 46 of the drill blanks fromreaching the hardening temperature during the heat treating operation,the mounting block 30 is provided and receives the drill blanks therein.As il lustrated in FIG. 2, the mounting block 30 is formed of a ceramicfiber material of special construction and is comprised essentially of51.2 percent aluminum oxide and 47.4 percent silicon oxide. The ceramicfiber material of the block 30 is defined by short staple fibers thatare compressed together to form the mass as indicated. In order to mountthe drill blanks in vertical position in the block 30 during the heattreating operation, a plurality of holes 48 are bored therein, each ofthe holes 48 receiving a metallic insert 50 therein. The metallicinserts are formed of a mild steel material and have a central opening52 extending therethrough, the diameter of which is adapted toaccommodate a drill shank therein. It is seen that when the drill blanksare mounted in the block 30 for the heat treatment thereof, the shankportions 46 of each drill is embedded in a metallic insert, the fluteportions extending above the block and being directly exposed to thehigh temperatures generated in the heat treating chamber 13.

In preparing for the heat treating of the drill blanks or any othermetallic article that is to be heat treated in the furnace 10, it isfirst desirable to condition the ceramic fiber block 30 so as to renderit inert, thereby preventing decarborization of the metallic articlessupported therein. The ceramic fiber block is cleansed by placing it inthe furnace chamber and bringing the temperature of the heating chamber13 up to normal operating temperatures. The impurities in the ceramicfiber blockare thus removed, and the block is rendered substantiallyinert for all practical purposes.

After the ceramic fiber block has been preconditioned, the drill blanksare placed therein by locating the shanks 46 of the drill blanks in theinserts 50. The openings in the block 30 and the length of the inserts50 are such that the shanks of the drills are effectively insulated,whereas the flute portions 44 are exposed and extend above the uppersurface of the ceramic fiber block 30. With the ceramic fiber block 30located in the basket 28 and the basket disposed on the tray 26, thetray is pushed into the heating chamber 13 to the position asillustrated in FIG. 1. The heat treatment operation is then carried out,wherein the flute portions 44 of the drill blanks are brought up to theaustenitizing temperature so as to provide for bright hardening thereof.After the heating cycle is completed, the door 16 is opened and the tray26 is then pushed by a hand or cylinder operated push rod from theheating chamber 14 through the duct 17 and into the cooling chamber 19.This operation is quickly carried out, and the fan 20 is then operatedto circulate the conditioning atmosphere entering into the coolingchamber 19 through the inlet 22. By rapidly circulating the atmospherein the cooling chamber 19 the metallic articles are cooled quicklyenough so that sufficient heat is removed therefrom to prevent theirshank portions 46 from reaching the austenitizing or hardeningtemperature.

It is seen that the process by which the metallic articles are heatedand cooled in the apparatus of the subject invention, the flute portions44 of the articles are bright hardened while the lower shank portions 46thereof are maintained relatively soft so that they may be marked foridentification by stamping the drill size and other identifying indiciathereon. The forced atmosphere recirculating in the cooling chamberwherein the atmosphere is moved over and around the drill blanks removesthe heat therefrom in the shortest possible time and since the heatingcycle is controlled such that the flute portions are heated justsufficiently to be brought up to the austenitizing temperature, thesupporting ceramic fiber blockand the metal inserts are thus onlypartially heated to this temperature. This being the case, the shankportions 46 of the drill blanks are also only partially heated to theaustenitizing temperature; and when the block 30 with the drill blankstherein are moved into the cooling chamber, the heat is removedtherefrom quickly enough to prevent the shanks of the drills fromreaching the hardening temperature. Marking of the drill shanks foridentification by stamping is then carried out without any additionalprocedures necessary, since the drill shanks are still soft enough topermit ready marking thereon.

Although the present invention has been described in connection with theheat treatment of metallic articles, such as drills, it is alsounderstood that other metallic articles can be heat treated in a similarmanner, particularly when it is desired to maintain a portion of thearticles in a relatively soft condition for marking. It is alsounderstood that the articles may be disposed other than in a verticalposition as long as a portion thereof is protected in the ceramic fiberblock. While there is shown and described herein certain specificstructure embodying the invention, it will be manifest to those skilledin the art that various modifications and rearrangements of the partsmay be made without departing from the spirit and scope of theunderlying inventive concept and that the same is not limited to theparticular forms herein shown and described except insofar as indicatedby the scope of the appended claims. 1

What is claimed is: t

r 1. Apparatus for heat treating a metallic article in a furnace,wherein the article includes a first portion and a second portionintegrally joined to said first portion and the furnace includes aheating chamber in which the metallic article is heat treated,comprising a ceramic block having a plurality of vertically disposedopenings formed therein that are laterally spaced apart in said block, ametallic insert formed of mild steel being mounted in each opening andextending inwardly for a substantial portion thereof, wherein the insertas located in each opening is substantially vertical, a verticallydisposed opening formed in each of the inserts and having a diameter thedimension of which is sufficient to slidably receive the first portionof a metallic article, the first portion of the article being insulatedin said insert during the heat treating operation, the

second portion of each article that defines the working portion of thearticle and that is to be hardened being exposed above the block, and aholder for said block that is receivable within said furnace heatingchamber, wherein the block and the articles retained in the metallicinserts therein are entirely enclosed in the heating chamber during theheat treating operation.

1. Apparatus for heat treating a metallic article in a furnace, whereinthe article includes a first portion and a second portion integrallyjoined to said first portion and the furnace includes a heating chamberin which the metallic article is heat treated, comprising a ceramicblock having a plurality of vertically disposed openings formed thereinthat are laterally spaced apart in said block, a metallic insert formedof mild steel being mounted in each opening and extending inwardly for asubstantial portion thereof, wherein the insert as located in eachopening is substantially vertical, a vertically disposed opening formedin each of the inserts and having a diameter the dimension of which issufficient to slidably receive the first portion of a metallic article,the first portion of the article being insulated in said insert duringthe heat treating operation, the second portion of each article thatdefines the working portion of the article and that is to be hardenedbeing exposed above the block, and a holder for said block that isreceivable within said furnace heating chamber, wherein the block andthe articles retained in the metallic inserts therein are entirelyenclosed in the heating chamber during the heat treating operation.